I’m using Blender 3.4.1 and Uefy 2.5 at the time of this writing and it works correctly.
When you first click on “Generate Rig” blender will create an armature object named “rig”. After clicking “Build Skeleton” Uefy will process that object and rename it as “Armature”. The rename is important for correct export to Unreal Engine.
After you modify the metarig and run “Re-Generate Rig”. At this point the armature object is still named “Armature”, so just click on the refresh list button and set the rig field to “Armature”.
You can always check the list of objects in the scene to check the current name of the armature object.